Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session P25: Focus Session: Graphene VII: Electronic Properties |
Hide Abstracts |
Sponsoring Units: DMP Chair: Andre Geim, Manchester University Room: 327 |
Wednesday, March 18, 2009 8:00AM - 8:12AM |
P25.00001: Cyclotron Resonance at the Dirac Point Paul Cadden-Zimansky, Erik Henriksen, Zhigang Jiang, Li-Chun Tung, Mollie Schwartz, Yong-Jie Wang, Philip Kim, Horst Stormer We present high field infrared spectroscopy data on the n = -1 $\rightarrow$ 0 and n = 0 $\rightarrow$ 1 Landau Level (LL) transitions in graphene. At high magnetic fields, up to 31 T, measurements of single layer graphene show large shifts in the transition energies, which are suggestive of a gap in the n = 0 LL. The magnitude of these shifts are strongly enhanced over the bare Zeeman splitting naively expected for a spin-split state. We compare the field dependence of the shifts with proposed degeneracy-breaking mechanisms at the Dirac point. [Preview Abstract] |
Wednesday, March 18, 2009 8:12AM - 8:24AM |
P25.00002: Hydrodynamic approach to transport in graphene Rafi Bistritzer, Allan MacDonald Exploiting the strong electron-electron interactions in graphene we construct a hydrodynamic theory in which the carrier dynamics is described by three parameters: the electronic temperature, the chemical potential and the drift velocity. We use this theory to describe both linear and non linear transport in graphene. [Preview Abstract] |
Wednesday, March 18, 2009 8:24AM - 9:00AM |
P25.00003: Graphene Update Invited Speaker: Graphene is now a bright and still rapidly rising star on the horizon of materials science and condensed matter physics, revealing a cornucopia of new physics and potential applications [1]. I will overview our recent experimental work on graphene concentrating on its exotic electronic properties and speculate about potential applications. References [1] For review, see A. K. Geim, K. S. Novoselov. Nature Mater. 6, 183 (2007). [Preview Abstract] |
Wednesday, March 18, 2009 9:00AM - 9:12AM |
P25.00004: Energy Relaxation of Hot Dirac Fermions in Graphene Wang-Kong Tse, Sankar Das Sarma We develop a theory for the energy relaxation of hot Dirac fermions in graphene. We obtain a generic expression for the energy relaxation rate of hot Dirac fermions in graphene due to electron-phonon interaction and calculate the power loss due to both optical and acoustic phonon emission as a function of electron temperature $T_{\mathrm{e}}$ and density $n$. We find an intrinsic power loss weakly dependent on carrier density and non-vanishing at $n = 0$, originating from interband electron-optical phonon scattering from the intrinsic electrons in the graphene valence band. We also obtain the total power loss per carrier to be $\sim 10^{-12}\,-\,10^{-7}\,\mathrm{W}$ within the range of electron temperatures $\sim 20\,-\,1000\,\mathrm{K}$, finding that the temperature for the optical phonon emission to overtake acoustic phonon emission as the dominant energy loss mechanism ranges $\sim 200-300\,\mathrm{K}$ for $n = 10^{11}-10^{13}\,\mathrm{cm}^{-2}$. [Preview Abstract] |
Wednesday, March 18, 2009 9:12AM - 9:24AM |
P25.00005: Electron and hole puddles in monolayer graphene on SiO$_{2}$ B.J. LeRoy, A. Deshpande, W. Bao, F. Miao, C.N. Lau We have performed spatially resolved scanning tunneling spectroscopy measurements on single layer graphene. The graphene was prepared on SiO$_{2}$ by the mechanical exfoliation technique and an electrode was attached by electron beam lithography. Atomically resolved topography images over 40 nm areas show that the graphene conforms to the SiO$_{2}$ surface as well as having intrinsic ripples. In addition to the topography measurements, we have mapped the local density of states as a function of position and energy. We observe a spatially varying Dirac point which leads to electron and hole puddles at low energy. These puddles have a characteristic size scale of about 5 nm. The puddles arise due to curvature in the graphene film which induces shifts in the chemical potential as well as long range scattering from charged impurities. [Preview Abstract] |
Wednesday, March 18, 2009 9:24AM - 10:00AM |
P25.00006: Ripples on graphene and their effect on lattice and electronic properties Invited Speaker: A discovery of graphene, a new allotrope of carbon [1], representing the simplest, one-atom thick, membrane, opens exciting perspectives in statistical physics of two-dimensional systems in general. As expected from theory of flexible membranes [2], free suspended graphene is corrugated (rippled) due to thermal bending fluctuations, which was confirmed by experiment [3] and atomistic simulations [4]. This makes graphene strongly anharmonic crystal leading to anomalous temperature dependences of its thermal expansion, elastic moduli and other thermodynamic and mechanical properties. The ripples are also a source of pseudomagnetic gauge field [5] acting on Dirac fermions which leads to important consequences for the electronic structure such as a formation of midgap states [6,7]. Quenched ripples can be also important sources of electron scattering limiting charge-carrier mobility in graphene [8]. Possible mechanisms of this quenching are discussed. \\[3pt] [1] K.S. Novoselov et al, Science \textbf{306}, 666 (2004). \\[0pt] [2] \textit{Statistical Mechanics of Membranes and Surfaces}, ed. by D. R. Nelson, T. Piran, and S. Weinberg (World Sci, Singapore 2004). \\[0pt] [3] J.C. Meyer et al, Nature \textbf{446}, 60 (2007). \\[0pt] [4] A. Fasolino, J.H. Los, and M.I. Katsnelson, Nature Mater. \textbf{6}, 858 (2007). \\[0pt] [5] S.V. Morozov et al, Phys. Rev. Lett. \textbf{97}, 016801 (2006). \\[0pt] [6] F. Guinea, M.I. Katsnelson, and M.A.H. Vozmediano, Phys. Rev. B \textbf{77}, 075422 (2008). \\[0pt] [7] T.O. Wehling et al, Europhys. Lett. \textbf{84}, 17003 (2008). \\[0pt] [8] M.I. Katsnelson and A.K. Geim, Phil. Trans. Royal Soc. A \textbf{366}, 195 (2008). [Preview Abstract] |
Wednesday, March 18, 2009 10:00AM - 10:12AM |
P25.00007: Rippling of Graphene Maria Moura, Rebecca Thompson-Flagg, Michael Marder Experiments found that free standing single-layer graphene sheets display ripples (see ref. Meyer et al. Nature 446, 60 2007). Here we show that these ripples can be a consequence of adsorbed molecules sitting on random sites. The adsorbates cause the bonds between the carbon atom to lengthen slightly. Static buckles caused by roughly 20 \% coverage of adsorbates are consistent with experimental observations. We explain why this mechanism is more likely to explain ripples than are thermal fluctuations or the Mermin-Wagner theorem (previously invoked). [Preview Abstract] |
Wednesday, March 18, 2009 10:12AM - 10:24AM |
P25.00008: Spectromicroscopy study of surface morphology and quasiparticle dynamics in suspended graphene Kevin Knox, Mehmet Yilmaz, Shancai Wang, Alberto Morgante, Dean Cvetko, Andrea Locatelli, Onur Mentes, Miguel Nino, Philip Kim, Richard Osgood We report angle-resolved photoemission and electron diffraction measurements of single crystal exfoliated graphene obtained at the Nanospectroscopy beamline at the Elettra synchrotron light source. Although typical exfoliated graphene sample sizes prohibit the use of conventional UHV techniques, we have used micro-spot low-energy electron diffraction ($\mu $LEED) and micro-spot angle-resolved photoemission ($\mu $ARPES) to probe this unique 2D system. $\mu $LEED measurements provide information about the surface morphology of monolayer and multilayer graphene sheets, which are not atomically flat, but microscopically corrugated. Our photoemission measurements reveal details of the quasiparticle spectrum in the vicinity of the Fermi level. We will discuss modifications to the bare band dispersion due to electron-electron interactions and departure from the standard Fermi liquid model for quasiparticle lifetime. Results from suspended graphene will be compared to results from samples supported on SiO$_{2}$. [Preview Abstract] |
Wednesday, March 18, 2009 10:24AM - 10:36AM |
P25.00009: Kohn-Luttinger superconductivity in graphene Jose Gonzalez We address the development of superconductivity in graphene when the Fermi level becomes close to one of the Van Hove singularities of the electron system. The different segments of the Fermi line show then an approximate nesting, which enhances unconventional superconducting and magnetic correlations for a dominant repulsive interaction. The origin of the pairing instability lies in the strong anisotropy of the e-e scattering along the Fermi line, leading to a channel with attractive coupling when making the projection of the BCS vertex on the symmetry modes with nontrivial angular dependence. We show that the superconducting instability is particularly strong at the Van Hove singularity in the valence band of graphene, where the critical scale may be pushed up to temperatures larger than 1 K, depending on the ability to tune the Fermi level to the proximity of the singularity. [Preview Abstract] |
Wednesday, March 18, 2009 10:36AM - 10:48AM |
P25.00010: Polarization and Spectral Properties of Massive Graphene Valeri Kotov, Vitor Pereira, Bruno Uchoa, Antonio Castro Neto We discuss the situation when a finite gap exists in the Dirac fermion spectrum, due to either external factors (substrate-induced), or the mesoscopic (finite size) nature of the sample. The gap could also be generated dynamically via chiral symmetry breaking. We will overview: (1.) The behavior of the polarization charge, induced by an external Coulomb source. The charge density exhibits an unconventional distribution is space, which we present in detail. The density variation could be observable in real experiments when an external ion is placed on the graphene sheet. (2.) The modification of the fermion self-energy; in particular, the large-N limit of the theory. We find that in this limit, which could be relevant for Graphene, the electronic dispersion is strongly renormalized at small energies. We discuss possible consequences of this behavior. [Preview Abstract] |
Wednesday, March 18, 2009 10:48AM - 11:00AM |
P25.00011: High-Mobility Dual-gated Graphene Field-Effect Transistors with Al$_{2}$O$_{3 }$Dielectric Seyoung Kim, Junghyo Nah, Insun Jo, Davood Shahrjerdi, Luigi Colombo, Zhen Yao, Emanuel Tutuc, Sanjay Banerjee The carrier mobility in graphene field-effect transistors (GFETs) is primarily dominated by the extrinsic impurity scattering, such as charged impurities in the dielectric. Therefore, the impact of a top-gate dielectric stack on the transport characteristics of graphene represents a key issue for high-performance GFETs. Here, we present the fabrication and characterization of dual-gated graphene FETs and dual-gated graphene devices with Hall bar geometry using Al$_{2}$O$_{3}$ as top-gate dielectric. We use a thin Al film as a nucleation layer to enable the atomic layer deposition of Al$_{2}$O$_{3}$. Our FETs show mobility values of over 6,000 cm$^{2}$/Vs at room temperature, a finding which indicates that the top-gate stack does not significantly increase the carrier scattering, and consequently degrade the device characteristics. We propose a device model to fit the experimental data with a single mobility value. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2025 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700